Research Areas

Perovskite solar cells (PSCs) are considered to be a revolutionary next-generation solar cell technology because of their remarkable photovoltaic features, including a low exciton binding energy (< 20 meV), high absorption coefficient (105 cm-1), long charge carrier diffusion length (>1𝜇m), tunable band gap (1.4-2.5 eV). These superior properties have soared the power conversion efficiency (PCE) from 3.8% in 2009 to 25.8% in 2023. Among different device structures, the inverted p-i-n structure exhibited unique features, such as the ability to fabricate at low temperatures, minimal hysteresis, and excellent operational stability. Unfortunately, the power conversion efficiency (PCEs) of inverted PSCs still lag behind those of regular n-i-p structured devices. The limitation of hole transport layers (HTL) is deemed a major factor for restricting the performance of inverted PSCs, such as low conductivity, insufficient hole extraction, and photovoltage loss. Currently, the most commonly used HTLs are PEDOT: PSS, PTAA, and NiOX. Among those, NiOx holds great potential because of its lower cost, high optical transmittance, suitable charge carrier mobility, and superior chemical stability. However, the performance of NiOx-based PSCs faces several significant issues: 1) An interfacial energy level mismatch between NiOX and the perovskite causing a substantial energy offset; 2) Relatively low intrinsic conductivity of NiOx leading to charge accumulation and recombination at the interface; and 3) a lattice mismatch between the perovskite and NiOx induces strain, which aggravates the instability of the perovskite.

To addressed these above concerns involves the effective use of inorganic salts and organic molecules (polymers and small molecules) as buffer layers to regulate the NiOx-Perovskite interface, thereby improving PSC efficiency and stability.